A conventional header of this type generally includes a main drive shaft mounted on the rear of the main longitudinal beam of the header for communicating drive to one or more of the driven elements of the header including the knife drive of the cutter bar, the rotating reel and the transport means which transports the crop longitudinally of the header. It is of course necessary to communicate power from the tractor vehicle on which the header is transported to the main drive shaft.
The header can be mounted directly on a swather tractor in which case the mounting system includes arms which effect lifting of the header and in addition allow floating movement of the header to accommodate changes in ground height. It is also known to mount a header of this type on a reversible tractor so that the tractor is basically driven in reverse with an adapter specially provided between the three point hitch of the tractor and the header, the three point hitch providing vertical lift of the adapter and the header being mounted on the adapter for floating movement.
In both of these designs the tractor includes a PTO shaft which projects forwardly of the direction of movement of the tractor that is generally at right angles to the longitudinal beam of the header along which the drive shaft lies.
It is necessary, therefore, to provide an angle drive assembly which communicates the drive from the PTO shaft around approximately 90.degree. to the main drive shaft of the header. Generally this angled drive arrangement includes a right angle gear box mounted on the header frame with an input shaft which can tilt relative to the gear box to accommodate movement of the gear box relative to the PTO shaft. This drive is relatively complex and expensive leading to an overall increased cost for the manufacture of the machine.
A constant velocity (CV) joint is a well known construction which includes two universal joints arranged back to back with an interconnecting coupler. An input to one of the universal joints is taken from an input shaft and an output from the CV joint is taken from the output of the second universal joint. The coupler between the two universal joints rotates with the input and output but at a variable speed. The symmetry of the device allows the output to be rotated at constant speed relative to the input while the changes or variations in speed are accommodated in the coupler.
CV joints are regularly used to communicate drive from an input shaft to an output shaft at a relatively shallow angle between the input and output shafts. CV joints can accommodate changes in the angle between the input and output shafts. Designs are available of CV joint which allow the drive line angle to flex up to 50.degree. with a suitable lifetime of operation obtainable when the joint is normally maintained in the 0.degree. to 40.degree. range.
It is known to connect two CV joints back to back to provide an increased angle in the drive line of greater than 50.degree.. In addition joints are available which can accommodate flexing of the drive line up to 80.degree. but these joints are significantly more expensive.
Multiple universal joints have been used to transmit low power through angles greater than 90.degree.. For example a rod weeder is a conventional tillage cultivator with a rod supported across the back of the cultivator so that when the cultivator is engaged in the ground, the rod is just below the surface of the ground. The rod is rotated in the direction opposite to the ground wheel so that weeds are pulled out of the loose soil and deposited on top of the soil. The rod is usually driven by the cultivator wheels through a series of universal joints that transmit the power through an angle of approximately 180.degree..
Up till now it is believed that joints of this type have not been used in agricultural machines to provide communication through an angle of the order of 90.degree. of the significant amounts of power necessary to drive the elements of the header or the like.